linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 * Lockless hierarchical page accounting & limiting

 *

 * Copyright (C) 2014 Red Hat, Inc., Johannes Weiner

 */

​

#include <linux/page_counter.h>

#include <linux/atomic.h>

#include <linux/kernel.h>

#include <linux/string.h>

#include <linux/sched.h>

#include <linux/bug.h>

#include <asm/page.h>

​

static void propagate_protected_usage(struct page_counter *c,

                      unsigned long usage)

{

    unsigned long protected, old_protected;

    long delta;

​

    if (!c->parent)

        return;

​

    if (c->min || atomic_long_read(&c->min_usage)) {

        if (usage <= c->min)

            protected = usage;

        else

            protected = 0;

​

        old_protected = atomic_long_xchg(&c->min_usage, protected);

        delta = protected - old_protected;

        if (delta)

            atomic_long_add(delta, &c->parent->children_min_usage);

    }

​

    if (c->low || atomic_long_read(&c->low_usage)) {

        if (usage <= c->low)

            protected = usage;

        else

            protected = 0;

​

        old_protected = atomic_long_xchg(&c->low_usage, protected);

        delta = protected - old_protected;

        if (delta)

            atomic_long_add(delta, &c->parent->children_low_usage);

    }

}

​

/**

 * page_counter_cancel - take pages out of the local counter

 * @counter: counter

 * @nr_pages: number of pages to cancel

 */

void page_counter_cancel(struct page_counter *counter, unsigned long nr_pages)

{

    long new;

​

    new = atomic_long_sub_return(nr_pages, &counter->usage);

    propagate_protected_usage(counter, new);

    /* More uncharges than charges? */

    WARN_ON_ONCE(new < 0);

}